Surface Acoustic Wave Humidity Sensor Based on Hydrophobic Polymer Film

Memon, Maria Muzamil; Yu, Hongyuan; Pan, Shuliang; Wang, Tao; Zhang, Wanli

doi:10.1007/s11664-022-09791-5

Cited by 12 publications

(6 citation statements)

References 49 publications

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“…However, for some specific polymers, the absorption of water molecules hardens the polymer chain instead of the usual softening effect, known as antiplasticization or stiffening effect. This unusual hardening effect increases the velocity that causes the elastic effect contributes in the opposite direction to the mass loading effect, as observed for the fluorinated polyimide-based SAW humidity sensor [ 33 ]. Likewise, the positive shift was observed for the polyimide-coated SAW humidity sensor initially in lower ranges which was overwhelmed by the mass loading effect [ 34 ].…”

Section: Sensing Mechanismmentioning

confidence: 94%

“…Similarly, the change in permittivity was characterized as the main mechanism for cellulose acetate based humidity sensor [ 53 ]. However, some authors described the elastic effect as the main contributor [ 30 , 33 ]. In general, the overall response of the sensor is primarily defined by operational mechanisms, which depend on the physical and chemical properties of the sensing film and the influence of water vapor interaction on their intrinsic parameters such as mass density, thickness, conductivity, and elasticity.…”

Section: Sensing Materialsmentioning

confidence: 99%

“…Apart from physical parameters, the modification in the chemical properties of the sensing film can also aid in improving the sensing characteristics. In [ 33 ], the polyimide with hydrophobic characteristics was used as the humidity-sensing film to reduce the hysteresis issue. The fluorinated polyimide-coated humidity sensor exhibited negligible hysteresis compared to ordinary polyimide-coated sensors [ 43 , 57 ].…”

Section: Sensing Materialsmentioning

confidence: 99%

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Surface Acoustic Wave Humidity Sensor: A Review

et al. 2023

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The Growing demands for humidity detection in commercial and industrial applications led to the rapid development of humidity sensors based on different techniques. Surface acoustic wave (SAW) technology is one of these methods that has been found to provide a powerful platform for humidity sensing owing to its intrinsic features, including small size, high sensitivity, and simple operational mechanism. Similar to other techniques, the principle of humidity sensing in SAW devices is also realized by an overlaid sensitive film, which serves as the core element whose interaction with water molecules is responsible for overall performance. Therefore, most researchers are focused on exploring different sensing materials to achieve optimum performance characteristics. This article reviews sensing materials used to develop SAW humidity sensors and their responses based on theoretical aspects and experimental outcomes. Herein the influence of overlaid sensing film on the performance parameters of the SAW device, such as quality factor, signal amplitude, insertion loss, etc., is also highlighted. Lastly, a recommendation to minimize the significant change in device characteristics is presented, which we believe will be a good step for the future development of SAW humidity sensors.

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Section: Sensing Mechanismmentioning

confidence: 94%

Section: Sensing Materialsmentioning

confidence: 99%

Section: Sensing Materialsmentioning

confidence: 99%

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Surface Acoustic Wave Humidity Sensor: A Review

et al. 2023

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“…Repetitive cycles of testing (atleast 10 times) showed that the variation in the readings is within ± 3% error. It is well known that humidity has a major effect on the travelling of acoustic waves in SAW device [33]. When the device is exposed to a humid environment, condensed water on it affects the acoustic velocity which in turn causes resonant frequency shifts [34].…”

Section: Testing Of Device Under Various Temperature and Humidity Con...mentioning

confidence: 99%

Design optimization of surface acoustic wave devices and investigation of fabricated devices under temperature, humidity and steam environments

Anbalagan,

Lakshminarayanan,

Girija

2024

Phys. Scr.

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Surface Acoustic Wave (SAW) technique is one of the most promising Micro Electro Mechanical Systems (MEMS) based detection methods for a variety of applications. SAW sensor is based on the modulation of Rayleigh waves that travel near the surface of a piezoelectric substrate. Advent of MEMS technology has led to the development of SAW sensors which are widely used in chemical sensing, medical, industrial, telecommunication and biological applications. The main focus of this paper is to devise and characterize a generic SAW structure and study the acoustic properties at various environmental conditions before depositing the sensing layer/analyte for any particular application. In this work, a SAW device was designed using COMSOL Multiphysics for a resonant frequency of 100 MHz with 40 µm wavelength on Lithium Niobate (LiNbO3) piezoelectric substrate. The optimized device structure was fabricated using thin film deposition and UV photolithography. The resonant frequency of the fabricated device (97.63 MHz) matched closely with the simulation results (100 MHz) and theoretical results (100 MHz). The device was subjected to various environmental conditions to study the influence on the resonant frequency. The SAW structure showed a resonant frequency shift of 90 KHz in steam environment, ~ 1MHz when heated to 150°C and ~120 KHz when exposed to 80% RH. The device exhibited a linear shift in resonant frequency under all tested environmental conditions with a consistent baseline and good repeatability.

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“…Humidity measurement is critical in many branches of human activities such as industrial processes, agricultural productions, room and motor vehicles conditions, production of medicines as well the very precise research experiments. The most of the contemporary humidity sensors are based on the capacitance, resistance, impedance, acoustic and optical methods, however, their mutual drawback is often the low accuracy and hysteresis effect at the low humidity detection levels [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]. Considerable efforts have thus been focused on the development of highly sensitive materials and novel device structures to address these issues [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ].…”

Section: Introductionmentioning

confidence: 99%

SAW Humidity Sensing with rr-P3HT Polymer Films

Jakubik,

Wrotniak,

Caliendo

et al. 2024

Sensors

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In the present paper the humidity sensing properties of regioregular rr-P3HT (poly-3-hexylthiophene) polymer films is investigated by means of surface acoustic wave (SAW) based sensors implemented on LiNbO3 (1280 Y-X) and ST-quartz piezoelectric substrates. The polymeric layers were deposited along the SAW propagation path by spray coating method and the layers thickness was measured by atomic force microscopy (AFM) technique. The response of the SAW devices to relative humidity (rh) changes in the range ~5–60% has been investigated by measuring the SAW phase and frequency changes induced by the (rh) absorption in the rr-P3HT layer. The SAW sensor implemented onto LiNbO3 showed improved performance as the thickness of the membrane increases (from 40 to 240 nm): for 240 nm thick polymeric membrane a phase shift of about −1.2 deg and −8.2 deg was measured for the fundamental (~78 MHz operating frequency) and 3rd (~234 MHz) harmonic wave at (rh) = 60%. A thick rr-P3HT film (~600 nm) was deposited onto the quartz-based SAW sensor: the sensor showed a linear frequency shift of ~−20.5 Hz per unit (rh) changes in the ~5–~50% rh range, and a quite fast response (~5 s) even at low humidity level (~5% rh). The LiNbO3 and quartz-based sensors response was assessed by using a dual delay line system to reduce unwanted common mode signals. The simple and cheap spray coating technology for the rr-P3HT polymer films deposition, complemented with fast low level humidity detection of the tested SAW sensors (much faster than the commercially available Michell SF-52 device), highlight their potential in a low-medium range humidity sensing application.

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Surface Acoustic Wave Humidity Sensor Based on Hydrophobic Polymer Film

Cited by 12 publications

References 49 publications

Surface Acoustic Wave Humidity Sensor: A Review

Surface Acoustic Wave Humidity Sensor: A Review

Design optimization of surface acoustic wave devices and investigation of fabricated devices under temperature, humidity and steam environments

SAW Humidity Sensing with rr-P3HT Polymer Films

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